<!DOCTYPE html>  
<html lang="zh-CN">  
<head>  
    <meta charset="UTF-8">  
    <meta name="viewport" content="width=device-width, initial-scale=1.0">  
    <title>CSS 盒子模型示例</title>  
    <style>  
        .box {  
            width: 200px;                
            height: 100px;            
            padding: 20px;             
            border: 5px solid black;      
            margin: 30px;               
            background-color: lightblue;   
        }  
    </style>  
</head>  
<body>  
    <div class="box">  
        盒子模型示例。  
    </div>  
</body>  
</html>